Chlorosulfonated block copolymers

ABSTRACT

Block copolymers are provided which have the properties of a vulcanized polymer without chemical crosslinking. These block copolymers comprise chlorosulfonated derivatives of block polymers having alternate monovinyl arene polymer blocks and chlorosulfonated polymer blocks of the group consisting of polyethylene and hydrogenated polybutadiene.

United States Patent Shaw 1 Sept. 26, 1972 4] CHLOROSULFONATED BLOCK-[56] References Cited ACOPOLYMERS UNITED STATES PATENTS [72] Inventor:Alfred W. Shaw, Moraga, Calif.

- n ;3,607,979 9/1971 Winkler ..260/878 B Assisnee= Shell Oil p y, NewYork, Primary Examiner-Joseph L. Schofer F Assistant Examiner-A. Holler[22] Filed: Ju'y 31 1970 Attorney-Martin S. Baer and William H. Myers[2]] Appl. No.: 60,145 [57] ABSTRACT Block copolymers are provided whichhave the pro- "260/878 3,260,793 perties of a vulcanized polymer withoutchemical crosslinking. These block copolymers comprise [51] Int. Cl...C08f 19/04, C08f 19/08 If d d f bl l Field of Search ..260/878 B, 880B, 79.3 R chhms mate Wes ymers havmg alternate monovinyl arene polymerblocks and chlorosulfonated polymer blocks of the group consist- 1CHLOROSULFQNATED BLOCK COPOLYMERS BACKGROUND OF THE INVENTION A largenumber of polymers have been studied which have the general structure ofblock copolymers. A substantial number of derivatives of thebasicpolymers have been synthesizedprimarilyfor the purpose of creatingterminal polar reactive sites useful .for coupling or crosslinking.Special classes of these block copolymers have been found which arereferred toas self-vulcanizing block copolymers in that they exhibit thestress-strain properties of vulcanized polymers without having beensubjected to any chemical crosslinking operations. The typical blockcopolymer of this type has the structurepolystyrene-polyisoprenepolystyrene. Within certain limitations theseare elastomeric but as the polystyrene proportion increases theproperties gradually become those of a thermoplastic polymer.

A number of chlorosulfonated polymers have been synthesized, primarilythe chlorosulfonation products of polyethylene. These are especiallyuseful as highly stable textile coatings but may be used in electricalapplications, building products and the like. However, in

order to be useful for most end purposes it is necessary to vulcanizethese chlorosulfonated polyethylenes with such vulcanizing agents asmagnesium oxide and the like. This entails an extra step in theirpreparation which adds to their cost and actually excludes them fromcertain end uses where the vulcanizing must be done in situ but the enduse will not tolerate this particular process.

It is an object of the present invention to provide improved blockcopolymers. It is a particular object of the invention to provide oilresistant and age resistant block copolymers which do not requirevulcanization. It is a further objectof the invention to providematerials suitable for use in compositions intended for waterpurification processes and the like. Other objects will become apparentduring the following detailed description of the invention.

STATEMENT THE INVENTION Now, in accordance with the present inventionchlorosulfonated block copolymers are provided comprising alternateblocks of monovinyl arene polymer blocks and chlorosulfonated polymerblocks of the group consisting of polyethylene blocks and polybutadieneblocks. Preferably, the chlorosulfonated polymer blocks have a sulfurcontent in the order of 05-10 percent and a chlorine content betweenabout 5 and 35 percent both by weight. Still in accordance with thisinvention, it has been found that the chlorosulfonated polymers of thisparticular type have highly desirable properties relative to oilresistance, flame resistance, ozone resistance, and age resistance,indicating their utility in situations capitalizing upon these improvedproperties. Moreover, it has been found that these chlorosulfonatedpolymers do not require vulcanization in order to attain and retain thestress-strain properties which are found to be especially desirable.

The block copolymers of the present invention are derived bychlorosulfonation of several types of precursor block copolymer. In allof these alternate polymer blocks are monovinyl arene polymer blockssuch as those of styrene, alpha-methyl styrene, or ring alkylatedstyrenes. The alternate blocks copolymerized with these are eitherhydrogenated polybutadiene or polyethylene blocks. It is particularlycontemplated that the polybutadiene blocks have no more than aboutpercent 1,2-content so as to closely resemble polyethylene whenhydrogenated to an extent of at least about 70 percent of its olefmiclinkages. Thus the block copolymers of this invention prior tochlorosulfonation are essentially non-elastomeric" since each of thepolymer blocks contained therein has glass transition temperaturesubstantially above room temperature. The precursor block copolymers maybe either linear or branched, i.e., star-shaped, radial, etc. They maybe formed by coupling reactions or by sequential block copolymerization.Preferably the monovinyl arene polymer blocks have average molecularweights between about 10,000 and 25,000 and the chlorosulfonated polymerblocks have average molecular weights prior to chlorosulfonation in theorder of 40,000 to 150,000. The simplest structure contemplated has thegeneral configuration A-B-A. However, the general structure ofmulti-block linear configuration is A-(-B-A),,, while the generalcontemplated branched structure may be represented by the generalconfiguration A-B-(-B-A),,. In the above configurations whereveradjacent blocks are represented by the same letter, e.g., B, theseimmediately adjacent blocks are reare concerned and insofar as alternateblocks are concerned. In the above general configurations the subscriptIt represents an integer usually between 1 and 5. Two particularlycontemplated basic configurations therefore comprise in their simplestrepresentation polystyrene-polyethylene-polystyrene orpolystyrenehydrogenated polybutadiene-polystyrene.

The preparation of the block copolymers which are used to form thechlorosulfonated derivatives does not form a part of the presentinvention. Briefly, however, they may be prepared by several alternativeprocesses such as the solution process utilizing a lithium alkylinitiator or a polylithium hydrocarbyl compound. When employing alithium alkyl such as lithium butyl, the first stage preferablycomprises the polymerization of a monovinyl arene to form a first livingmonovinyl arene polymer block. Subsequently and without removing thelithium ion associated with the living polymer block, butadiene isinjected into the system preferably in the absence of any polarcompounds so as to maintain as high a cis 1,4-structure as possible andpolymerization continued to form an intermediate living copolymer blockgenerally represented as A-B-Li. Two alternatives then may be chosen forforming the block copolymers of this invention, namely, either couplingthe intermediate living block copolymer or block polymerizingsequentially a second block of a monovinyl arene. In the latter case alinear polymer would be formed. When a coupling reaction is employed,the choice then exists of selection of the functionality of the couplingagent to result in either a linear block copolymer or one having abranched configuration. If a difunctional coupling agent, such as adihaloalkane or alkene is employed, then the product will have thestructure strongly resembling the sequentially produced linear polymer.However, if poly-functional coupling agents are utilized such as silicontetrachloride or a diester of a dicarboxylic acid and a monohydricalcohol, e.g., diethyl adipate, then nonlinear structures are obtained.

Subsequent to the formation of the precursor block copolymer, it issubjected to hydrogenation insofar as the center block is concerned andonly if the center block is butadiene. One of the requirements forhydrogenation of an unsaturated butadiene polymer block is to reduce itssensitivity insofar as the olefinic linkages are concerned which are aptto rupture during the chlorosulfonation step. The hydrogenation of thebutadiene polymer block results in what may be regarded as essentially apolyethylene block particularly if hydrogenation is carried to an extentof reducing at least about 70 percent of the olefinic unsaturationoriginally present in this block. if the olefinic block comprisespolyethylene, no hydrogenation, of course, is necessary.Chlorosulfonation of the olefinic block, i.e., either polyethylene orhydrogenated polybutadiene, is selective since monovinyl arene polymerblocks appear to be largely insensitive to the usual conditions ofchlorosulfonation. Two general methods may be employed. One involves theuse of sulfur dioxide and chlorine in the presence of light or a freeradical source, while the other utilizes sulfuryl chloride in thepresence of light and a small amount of catalyst such as pyridine orquinoline. The first method is preferred if it is desired to introducelarge amounts of chlorine with only small amounts of sulfur. The secondmethod is best suited to give reproducible results when a minimum amountof chlorine is desired.

Essentially all of the available chlorine ends up in the polymer whensulfuryl chloride is used as the chlorosulfonating agent. The yield onsulfur varies with the conditions and catalyst. Yields are improved bycontrolling the temperature preferably between and 30 C, althoughsatisfactory results are obtained at temperatures between about 20 and60 C. Suitable catalysts comprise diethyl amine, triethyl phosphate,amyl amine, or tributyl phosphine. Solvents preferred for thechlorination include halocarbons, such as carbon tetrachloride or arenessuch as benzenes.

The chlorosulfonated products prepared as described above may beutilized without vulcanization or further derivatizing although it ispossible and sometimes preferred to saponify the sulfonic acid groupswith either amines or alkali metals. The structure of the blockcopolymer is such that vulcanization is unnecessary since it will assumea suitable set of physical properties created by the domains set-up bythe monovinyl arene polymer blocks.

The chlorosulfonated polymers may be exposed to an atmosphere ofammonia. They may be converted to esters such as the phenyl esters.Typically this can be done by reacting the chlorosulfonated polymer withphenol in the presence of a solvent such as benzene and a catalyst suchas pyridine. Suitable reaction times are 4-48 hours at temperaturesbetween about 20 and 75 C. This results in increased stiffness of theproduct.

Amides of the chlorosulfonated polymers may be formed by reaction withprimary or secondary amines, particularly aliphatic mines. These reactnearly quantitatively with chlorosulfonated block copolymers, utilizinga reaction time in the order of 1-24 hours at ambient temperatures;preferably 100 percent or greater molar excess of the amine is employed.

The chlorosulfonated products of this invention have the propertiesnormally associated with thermoplastic polymers as contrasted toelastomeric polymers. They will have glass transition temperatures aboveroom temperature and no glass transition temperature at 50 C or lowersuch as typical of elastomeric products.

The subject type of chlorosulfonated block copolymers may be used assuch or blended with other polymers particularly chlorosulfonatedpolymer to alter the properties of the latter and to enhance theirutility in end uses such as electrical coverings, hoses, belting,sidewalls, building products, fabric coatings, or soling materials. Theyare particularly outstanding in their flame resistance, oil resistance,ozone resistance and age resistance as well as having a variable amountof hydrophilic properties depending upon the amount of chlorosulfonationwhich has taken place.

The following example illustrates the preparation of the chlorosufonatedproducts of this invention.

EXAMPLE 1 A block copolymer having the structurepolystyrenepolybutadiene-polystyrene is formed wherein the block averagemolecular weights are l5,00075,000l 5,000. The l,2-content of thepolybutadiene block is about 20 percent. This block copolymer ishydrogenated utilizing the reaction of aluminum triethyl and nickelacetate at temperatures in the order of about 30 C so as to selectivelyhydrogenate completely the polybutadiene block. The hydrogenated polymerthen subjected to chlorosulfonation under the following conditions:Block copolymer (25 grams) is dispersed in carbon tetrachloride (925grams), purged with nitrogen at 60 C for 15 minutes, cooled to 20 C.Thereafter, pyridine (0.2 cc) and sulfuryl chloride (10cc) are added.chlorosulfonation occurs at 20-30 C with the aid of ultraviolet lightfrom a 275 watt sunlamp for about 1 hour. Residual gases are then purgedfrom the system with nitrogen at about 50 C. The polymer is coagulatedin isopropyl alcohol and dried.

A pressed sample of this polymer has the following typical properties:

Tensile strength at Break 3000 psi Elongation at Break 300 Resilience 60Hardness (Shore A) 55 I claim as my invention:

1. A non-elastomeric thermoplastic chlorosulfonated block copolymer,having glass transition temperatures above room temperature and no glasstransition temperature below 50 C said copolymer comprising alternateblocks of (a) a monovinyl arene polymer and (b) of a thermoplasticnon-elastomeric polymer block of the group consisting ofchlorosulfonated polyethylene and chlorosulfonated hydrogenatedpolybutadiene, the latter block prior to hydrogenation having less than30 percent l,2-content said blocks (b) having a sulfur content betweenabout 0.5 percent and 10 percent and a chlorine between about 5 percentand 35 percent by weight.

2. A copolymer according to claim 1 wherein the alternating blocks arepolystyrene and chlorosulfonated polyethylene blocks.

alkali metal-neutralized sulfonic acid radicals.

6. A block copolymer according to claim 1 having the general structurewherein each A is a monovinyl arene polymer block, each B is achlorosulfonated polymer block and n is an integer from 1 to 5.

* IF l

2. A copolymer according to claim 1 wherein the alternating blocks arepolystyrene and chlorosulfonated polyethylene blocks.
 3. A copolymeraccording to claim 1 wherein the alternating blocks are polystyrene andchlorosulfonated hydrogenated polybutadiene blocks.
 4. A block copolymeraccording to claim 1 wherein the blocks (a) have average molecularweights between about 10,000 and 25,000 and the blocks (b) have averagemolecular weights between about 40,000 and 150,000.
 5. A block copolymeraccording to claim 1 bearing alkali metal-neutralized sulfonic acidradicals.
 6. A block copolymer according to claim 1 having the generalstructure A-B-(-B-A)n wherein each A is a monovinyl arene polymer block,each B is a chlorosulfonated polymer block and n is an integer from 1 to5.